This grant supports research in two areas: fetal opiate dependence and withdrawal, and the placental transfer of opiates. Studies are performed on chronically catheterized pregnant ewes. Opiate dependence is produced by continuous infusions of morphine into the mother. Opiate withdrawal is precipitated by intravenous injections of naloxone into the fetus and mother. Physiologic responses are measured. The specific effects of maternal withdrawal on the fetus will be studied by the simultaneous infusions of morphine into the mother and naloxone into the fetus. This will block the development of dependence in the fetus. Opiate dependence in the newborn lamb will be studied. Comparisons will be made between opiate withdrawal in the fetus and in the newborn lamb. Attempts will be made to block the development of dependence in the fetus so that withdrawal, or the lack thereof, can be studied in the newborn.